POS1442 THE PREVALENCE OF RHEUMATOID ARTHRITIS IN WESTERN AUSTRALIA EXTRAPOLATED FROM HOSPITALISATION AND BIOLOGICAL THERAPY USAGE DATA
Authors: K. Almutairi, C. Inderjeeth, D. Preen, H. Keen, J. Nossent
Journal: Annals of the Rheumatic Diseases (2022)

Background Rheumatoid arthritis (RA) is a heterogeneous chronic autoimmune disease that affects the synovial joint lining and may result in permanent joint destruction, premature death, and socio-economic burden. 1 Although RA is one of Australia’s national health priority areas and gathering information about the RA burden of disease was one of the national action plans 2 , no published epidemiological study adequately describes RA prevalence and risk factors for frequent hospitalisations in Western Australia (WA) to date. An accurate prevalence estimate of this disease offers a framework for predicting present and growing healthcare service requirements in the future. 3 Objectives We estimated RA period prevalence and identified risk factors of frequent RA hospitalisations, using linked administrative health and state-specific Australian Pharmaceutical Benefits Scheme (PBS) datasets in WA from 1995–2014. Methods RA prevalence was calculated per 1000 hospital separations and biological therapy users. RA patients were identified in the WA linked health dataset using ICD codes 714.0–714.9 and M05.00–M06.99. Dispensing data on biological therapy for RA were obtained from PBS records and converted to defined daily doses/1000 population/day. Multivariate logistic regression was used to analyse risk factors for frequent RA hospitalisations (&gt;2/year), controlling for sex, age, and geographic locations. Results A total of 17,125 RA patients were admitted to WA hospitals between 1995–2014. The total number of RA hospital separations was 50,353, averaging three hospitalisations per patient over 20 years. The RA period prevalence was 3.4 per 1,000 separations (0.34%), while the RA period prevalence based on biological therapy use was 0.36%. The corrected RA prevalence based on biological therapy usage was 0.36% and 0.72% for the 2005–2009 and 2010–2014 periods, respectively (Table 1). Female gender, age 60–69 years, and living in rural areas were all risk factors for frequent RA hospitalisations. Table 1. Total number of Rheumatoid Arthritis patients in Western Australia taking a standard dose daily (DDD) of RA biological therapy from 1995 to 2014. Year Total RA bDMARDs utilisation (DDD/1000 population/day) WA general population Prevalence of RA bDMARDs use in WA population (%) Number of RA patients use standard dose daily of bDMARDs at WA 2003 0.01 1,952,741 0.00 14 2004 0.08 1,979,542 0.01 158 2005 0.16 2,011,207 0.02 329 2006 0.23 2,050,581 0.02 476 2007 0.31 2,106,139 0.03 643 2008 0.50 2,171,700 0.05 1,094 2009 0.60 2,240,250 0.06 1,338 2010 0.59 2,290,845 0.06 1,361 2011 0.63 2,353,409 0.06 1,475 2012 0.77 2,425,507 0.08 1,859 2013 0.66 2,486,944 0.07 1,649 2014 1.00 2,517,608 0.10 2,510 Abbreviations: bDMARDs, biologic disease-modifying anti-rheumatic drugs included Abatacept, Adalimumab, Certolizumab, Etanercept, Golimumab, Infliximab, Rituximab, Tocilizumab; DDD, defined daily doses; RA, Rheumatoid arthritis; WA, Western Australia. Conclusion Based on hospital and biological therapy data, the minimal prevalence of RA in Western Australia is 0.34–0.36%, which falls within the literature range. Older female RA patients in rural areas were more likely to be hospitalised, suggesting unmet needs in primary care access. References [1] Guo Q, Wang Y, Xu D, Nossent J, Pavlos NJ, Xu J. (2018) Rheumatoid arthritis: pathological mechanisms and modern pharmacologic therapies. Bone Res. 6, 15. [2] Australian Institute of Health and Welfare. (2006) National indicators for monitoring osteoarthritis, rheumatoid arthritis, and osteoporosis. pp. 55. AIHW, Canberra. [3]Hanly JG, Thompson K, Skedgel C. (2015) The use of administrative health care databases to identify patients with rheumatoid arthritis. Open access rheumatology: research and reviews. 7(6), 69-75. Acknowledgements The authors thank the data custodians of Hospital Morbidity Data Collection, Emergency Department Data Collection, the Death Registrations and staff at the Western Australian Data Linkage Branch to assist in the provision of data. Special thanks to the University of Western Australia to support KA with an Australian Government Research Training Program PhD Scholarship and the Australian Rheumatology Association WA for Research Fellowship Award. Disclosure of Interests Khalid Almutairi: None declared, Charles Inderjeeth Speakers bureau: Eli Lilly, David Preen: None declared, Helen Keen Speakers bureau: Pfizer Australia, Abbvie Australia, Johannes Nossent Speakers bureau: Janssen